Implement blackbox in Golang (#250)

* Initial release

pkg/bbutil/filestats.go

@@ -0,0 +1,130 @@
+package bbutil
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"time"
+)
+
+// DirExists returns true if directory exists.
+func DirExists(path string) (bool, error) {
+	stat, err := os.Stat(path)
+	if err == nil {
+		return stat.IsDir(), nil
+	}
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	return true, err
+}
+
+// FileExistsOrProblem returns true if the file exists or if we can't determine its existence.
+func FileExistsOrProblem(path string) bool {
+	_, err := os.Stat(path)
+	if err == nil {
+		return true
+	}
+	if os.IsNotExist(err) {
+		return false
+	}
+	return true
+}
+
+// Touch updates the timestamp of a file.
+func Touch(name string) error {
+	var err error
+	_, err = os.Stat(name)
+	if os.IsNotExist(err) {
+		file, err := os.Create(name)
+		if err != nil {
+			return fmt.Errorf("TouchFile failed: %w", err)
+		}
+		file.Close()
+	}
+
+	currentTime := time.Now().Local()
+	return os.Chtimes(name, currentTime, currentTime)
+}
+
+// ReadFileLines is like ioutil.ReadFile() but returns an []string.
+func ReadFileLines(filename string) ([]string, error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	s := string(b)
+	s = strings.TrimSuffix(s, "\n")
+	if s == "" {
+		return []string{}, nil
+	}
+	l := strings.Split(s, "\n")
+	return l, nil
+}
+
+// AddLinesToSortedFile adds a line to a sorted file.
+func AddLinesToSortedFile(filename string, newlines ...string) error {
+	lines, err := ReadFileLines(filename)
+	//fmt.Printf("DEBUG: read=%q\n", lines)
+	if err != nil {
+		return fmt.Errorf("AddLinesToSortedFile can't read %q: %w", filename, err)
+	}
+	if !sort.StringsAreSorted(lines) {
+		return fmt.Errorf("AddLinesToSortedFile: file wasn't sorted: %v", filename)
+	}
+	lines = append(lines, newlines...)
+	sort.Strings(lines)
+	contents := strings.Join(lines, "\n") + "\n"
+	//fmt.Printf("DEBUG: write=%q\n", contents)
+	err = ioutil.WriteFile(filename, []byte(contents), 0o660)
+	if err != nil {
+		return fmt.Errorf("AddLinesToSortedFile can't write %q: %w", filename, err)
+	}
+	return nil
+}
+
+// AddLinesToFile adds lines to the end of a file.
+func AddLinesToFile(filename string, newlines ...string) error {
+	lines, err := ReadFileLines(filename)
+	if err != nil {
+		return fmt.Errorf("AddLinesToFile can't read %q: %w", filename, err)
+	}
+	lines = append(lines, newlines...)
+	contents := strings.Join(lines, "\n") + "\n"
+	err = ioutil.WriteFile(filename, []byte(contents), 0o660)
+	if err != nil {
+		return fmt.Errorf("AddLinesToFile can't write %q: %w", filename, err)
+	}
+	return nil
+}
+
+// FindDirInParent looks for target in CWD, or .., or ../.., etc.
+func FindDirInParent(target string) (string, error) {
+	// Prevent an infinite loop by only doing "cd .." this many times
+	maxDirLevels := 30
+	relpath := "."
+	for i := 0; i < maxDirLevels; i++ {
+		// Does relpath contain our target?
+		t := filepath.Join(relpath, target)
+		//logDebug.Printf("Trying %q\n", t)
+		_, err := os.Stat(t)
+		if err == nil {
+			return t, nil
+		}
+		if !os.IsNotExist(err) {
+			return "", fmt.Errorf("stat failed FindDirInParent (%q): %w", t, err)
+		}
+		// Ok, it really wasn't found.
+
+		// If we are at the root, stop.
+		if abs, err := filepath.Abs(relpath); err == nil && abs == "/" {
+			break
+		}
+		// Try one directory up
+		relpath = filepath.Join("..", relpath)
+	}
+	return "", fmt.Errorf("Not found")
+}